difference between sadaquah & Zakaat

Sadaqah is a voluntary act of spending to obtain proximity to Allah and to relieve one`s situation of difficulty or sickness. Any amount may be given in sadaqah and can be given to family members also without restriction Zakaat is the fixed 2.5% per annum that is compulsory for those who have nisaab to give to those who do not have nisaab. The nisaab is about Rs 30 000 nowadays and may vary every year. As such, if someone had nisaab last Ramadhaan for instance and now for this Ramadhaan, his account exceed Rs 30 000, then 2.5% of the Net Current Asset should be given to the poor. But he cannot give to his father, mother and children (ascendants and descendants).